KR830002179B1 - Equipment for manufacturing record discs with holes in the center - Google Patents

Abstract

An injection moulding apparatus for use in producing centrally-apertured video disc records (10). The apparatus includes first and second mould halves (11, 17) reciprocally movable with respect to each other between a closed position, wherein the two mould halves are in proximity to each other and molten plastic material is injected into a planar, annular cavity defined therebetween to form the record disc, and an open position, wherein the two mould halves are spaced apart from each other and the moulded record disc can be removed. The moulding apparatus further includes first and second annular rings (41, 43) carried by the respective first and second mould halves and defining the outer perimeter of the cavity. The first mould half includes two plates (13, 15) reciprocally vable with respect to each other, with a plurality of compression springs in the form of polyurethane blocks (105) interposed between the two plates, to bias the two annular rings into compressive engagement with each other when a central aperture is being punched in the moulded record disc.

Description

Equipment for manufacturing record discs with holes in the center

1 is a cross-sectional view of the molding apparatus of the present invention shown in a closed state.

FIG. 2 is a cross sectional view taken along the line 2-2 of FIG. 4, wherein the shaped video disk has a central hole drilled therein and is moved to an intermediate position.

3 is a partial cross-sectional view of the FIG. 1 apparatus after being moved to the open position.

4 is a plan view of the first mold half of the present device, taken along line 4-4 of FIG.

FIG. 5 is a cross sectional view taken along line 5-5 of FIG. 4, showing a cross section of a portion of the means for allowing the first and second mold halves to align when the apparatus is in the closed state.

FIG. 6 is an enlarged cross-sectional view of a portion of the central clamp for securing the stamper to the lower plate, which is within circle 6 of FIG.

7 is an enlarged cross-sectional view of a portion of the annular ring of FIG.

8 is an enlarged cross-sectional view of a portion of an annular ring in another example of the present invention having a polished model plate instead of a model stamper.

FIELD OF THE INVENTION The present invention generally relates to molding devices, and more particularly to injection molding devices for producing record discs with a central hole, such as a video disc.

This apparatus is used in an injection molding machine, in which a closed position where molten disk material is injected into an annular cavity to form a video disk, and a parting line through the cavity is opened. The first and second mold halves reciprocate between an open position whereby the shaped video disc can be removed from the device. The annular cavity is formed by a pair of planar disk-shaped stampers fixed to a platen on each mold half.

After the ejected disc material has cured, the molding machine begins to move the two mold halves from the closed position to the open position. A special latch fixture in the device holds the dividing line closed, causing an initial separation movement to occur between the two plates on the first mold half. When the two plates are separated by a predetermined amount, the formed video disk center hole is drilled, and the latching mechanism opens the dividing line to eject the video disk.

Each stamper has a hole in the center and is fixed by a special center clamp on its inner circumference and by a special outer ring clamp on its outer circumference. When the melt is injected into the cavity, air is vented through a narrow gap between the stamper for the second mold half and the annular foot which is integral with the outer ring clamp for the first mold half and protrudes radially inward. do. Although such equipment is generally satisfactory in most cases, variations in the stamper thickness affect the size of the ventilation passages, which can cause undesirable variations in back pressure generated by the exhaust air.

Another drawback of the molding apparatus described above arises in that the stampers can only be replaced in the field by complex insertion processes. Stampers can sometimes be damaged by inadvertent friction because of the conventional difficulty in accurately positioning the stamper relative to the clamp. Another problem arises in that only one of the stampers usually has information to be molded into the disc and the other stamper has two stampers even though it is a blank dummy. Like the stamper with information, the model stamper is also subject to wear and tear damage, which is caused by fine foreign matter particles between the stamper and the lower platen.

The two mold halves are aligned with each other by a number of guide pins. The plurality of guide pins are located on one mold half and engage a corresponding bushing located on the other mold half. Although effective to keep the two mold halves properly aligned, sometimes the guide plate and bushings may be worn to the extent that some misalignment of the two mold halves can occur.

Another drawback of the sharp forming apparatus arises from the use of a latch fastening mechanism to keep the dividing line closed until the center hole is drilled into the shaped disc. The fastening mechanism includes a rotating latch member having a pin that engages a corresponding groove formed by two arms fixed to each half of the mold. The fasteners tend to wear and usually require periodic maintenance, and the mechanism is also somewhat more complicated than necessary to achieve its purpose. It can be seen from the foregoing that there is a clear need for a simple forming apparatus that can be used to produce a properly functioning video disc without being easily tolerated without precise tolerances, and the present invention fulfills this need.

The present invention is embodied in an improved molding apparatus for use in a reciprocating injection molding machine for producing a record disk with a central hole, such as a video disk. The device is capable of reciprocating between a closed position in which the melt is injected into an annular cavity in the form of a disk to form a disk, and an open position in which the dividing line of the apparatus passing through the cavity is opened to eject the shaped disk. It consists of first and second mold halves.

At least one surface of the annular cavity is formed by a planar disc shaped stamper mounted on one of the two mold halves.

The closed position of the device is formed by bonding between the first and second annular rings supported on the first and second mold halves. According to one feature of the invention, the inner circumferences of the first and second rings form the outer circumference of the annular cavity, the rings having a plurality of holes for venting air from the annular cavity when molten material is injected into the annular cavity. Has the means to form. Further, the size of the hole does not depend on the relative thickness of the stamper, and a predetermined back pressure for the injected material can be maintained.

More specifically, each annular ring has a planar joining surface for engaging the other, and the vents are formed by a plurality of radial channels formed in the joining surface of at least one of the two rings. In addition, the inner cones of the two rings are approximately equal in radius and slightly inclined so that the disk shaped by the selected one half of the two mold halves can be securely retained when the dividing line is opened.

The inner circumference of the ring associated with the stamper-mounted mold half is formed by an annular foot that projects radially inward to retain the outer circumference of the stamper. The foot is sized to allow the stamper to expand in the radial direction when heated by the melt injected into the cavity.

Each of the first and second mold halves has a disk-shaped platen with conventional cooling channels for conveying cooling fluid to remove heat from the molten disk material. According to another feature of the invention, the stamper is not mounted on its corresponding cooling platen, but on a separate plate that is removably mounted to the platen. Thus, complicated installation of the stamper can be achieved at a distance, and subsequently, the stamper-mounted removable plate can be fixed relatively easily to the cooling platen. Thus, the possibility of damage to the stamper is considerably reduced. In addition, when recording information on only one side of the molded disc, the apparatus has only a single stamper, and the opposite side of the annular cavity is formed by a removable plate-shaped blank surface. This surface can be adequately cured and thus suffers significantly less damage from wear and tear than with conventional model stampers used in prior art molding apparatus.

Temporary alignment of the two mold halves with respect to each other is achieved by a plurality of guide pins installed in one of the mold halves and engaged with corresponding bushings installed in the other mold halves. According to another feature of the invention, a more accurate alignment of the two mold halves is provided by special alignment means which are not subjected to sliding friction when the two mold halves reciprocate with each other, and thus the alignment The wear of the means is minimal. In particular, the alignment means has a plurality of frustoconical posts which project outwardly from one of the two mold halves and engage the corresponding recesses formed in the other mold halves. In one embodiment, the struts and recesses are formed in individual members that are screwed into a special socket formed in each mold half.

In order to facilitate the drilling of the central hole in the molded disc, two reciprocating plates are installed in the first half of the mold, one of which has a cooling platen and a removable plate, the other of which One is coupled to a reciprocating molding machine. In operation, the molding machine begins to separate the two mold halves after the applied disk material is injected into the annular cavity and cured. The device has special means to keep the dividing line closed during the initial separation movement of the molding machine so that two reciprocating lamp plates on the first mold half can be separated. The two plates are separated by a predetermined distance and then a central hole is drilled into the formed disc. Only after the hole is drilled can the dividing line be opened, and the molded disk with the hole properly drilled in the center can be removed.

According to yet another feature of the invention, the special means for keeping the dividing line closed until the central hole is drilled has a compression spring installed between two reciprocating plates on the first mold half. The spring biases the plate with a dense plate and the cooling platen which are in compression engagement with the second mold half until the two plates are sufficiently separated to puncture the holes. Subsequently, the continuous moving of the molding machine opens the dividing line so that the finished disk can be removed. The spring is advantageously made of a replacement polyurethane material and thus requires no maintenance.

Many other features and advantages of the invention will be apparent from the following detailed description of the preferred embodiments described in connection with the accompanying drawings which illustrate by way of example the principles of the invention.

In the drawings, in particular in FIG. 1, a molding apparatus is shown for use in combination with a conventional injection molding machine (not shown) for producing a video disc record 10 having a central hole. The apparatus is composed of a first mold half portion 11 having a substrate 13 and a carrier plate 15 and a second mold half portion 17 having a substrate 19 and a carrier plate 21.

The two plates 13, 15 of the mold halves 11 of the first mold half 11 with respect to each other between their closed position (figure 1) and their intermediate position, i. Reciprocating On the other hand, the two plates 19 and 21 of the second mold half 17 are firmly joined to each other by a plurality of circumferentially spaced apart bolts, one of which is shown in dashed line as 23. Temporary alignment between the two mold halves is achieved by a number of guide pins 25 (FIG. 2). The guide pin 25 is fixed to the substrate 13 of the first mold half 11 and is slidably accommodated in the bushings 27 and 29 of the carrier plates 15 and 21 of the first and second mold halves 11 and 17.

Substrates 13, 19 on two mold halves 11 and 17 are mounted on separate reciprocating parts on a standard injection molding machine (not shown). The molding machine has an intermediate position in which the center hole is drilled in the molded baro disk 10 from the closed position (FIG. 1) where the mold halves are in contact and molten plastic material is injected into the annular cavity 31 formed between the cut portions. Ie move the two mold halves successively to the punching position (Fig. 2) and to the open position (Fig. 3) where the dividing line between the two mold halves is open and the molded disc can be removed. It works.

The annular cavity 31 between the two mold halves 11 and 17 is a first and second disc-shaped stamper 33 detachably coupled to the carrier plate 15 of the first mold half and the carrier plate 21 of the second mold half, respectively. Formed by 35. The melt is injected into the cavity through a nozzle 37, which is part of the molding machine, and a spout bushing 39 provided on the substrate 13 of the first mold half.

As shown in FIG. 1, the closed position of the shaping device is determined by the crimp engagement between the first annular ring 41 and the second annular ring 43. FIG. The rings are supported on the first and second mold halves, respectively. According to one aspect of the invention, the inner circumferences of the first and second rings form the outer circumference of the annular cavity 31, which rings from the cavity when molten plastic material is injected into the annular cavity through the spout bushing 39. It has a means for forming a plurality of holes 45 for venting air. The cross-sectional size of each hole is determined so that a predetermined back pressure for controlling the flow of the injected material can be maintained regardless of the variation in the relative thickness of either of the two stampers 33 and 35. Thus, the injected material can be moved radially outward in the cavity at a predetermined speed.

More specifically, as shown in FIGS. 4 and 7, the first annular ring 41 has a planar joint surface 47 for engaging with the corresponding joint surface 49 on the second annular ring 43, and the vent 45 It is formed by at least one of the two rings, here a number of radial channels formed in the joining surface of the first ring.

The cross-sectional size of each vent extends a predetermined distance from the inner circumference of the rings as indicated by numeral 51. In addition, the inner circumferences of the two annular rings have almost the same radius, and when the dividing line of the device is opened, the shaped disc 10 can be held by one of the two mold halves, here the first mold halves 11. So that it is inclined about 10 degrees.

As shown in Fig. 7, the two annular rings 41 and 43 are actually the same shape except for the inclination of the vent 45 and the inner circumference of the ring. The inner circumference of each ring is formed by an annular foot 53 that projects radially inward to retain the outer circumference of the corresponding stamper 33 or 35. As enlarged at 54, the feet are spaced slightly above the lower stamper, allowing the stampers to expand radially without undue friction when heated by the molten plastic material injected into the cavity 31.

The melt becomes sufficiently viscous after contacting the relatively cold stamper and does not travel by a significant price into the narrow space 54 between the ring and its lower stamper or into one of the vents 45.

The two carrier plates 15, 21 have disc shaped plates 55, 57 with helical cooling channels 59 for conveying cooling fluid (not shown) to remove heat from the melt injected into the annular cavity 31. Each has it.

According to another feature of the invention, the stampers 33 and 35 are not fixed to their corresponding cooling platens 55 and 57 but to separate plates 65 and 65 which are removably mounted to each platen. Thus, a complicated process of mounting the stamper can be performed at a distance, and then a removable plate equipped with a stamper can be mounted on its corresponding cooling platen relatively quickly and easily. Thus, the possibility of damage to the stamper, for example by inadvertent wear and tear, can be significantly reduced.

As shown in FIG. 1, two stampers 33, 35 are secured to the corresponding removable plates 63, 65 by special center clamps 67, 69, the clamps being spaced on a plurality of circumferences as indicated by 71. It is mounted on plates 63 and 65 with screws apart. The two clamps are in fact identical, so that the structure of clamp 69 on one of the clamps, namely the second mold cut 17, only describes the structure of the corresponding stamper 35 in detail.

As shown in FIG. 6, the stamper 35 has an inner circumference forming a central hole, and the corresponding central clamp 69 for the stamper has a cylindrical post 73 protruding upwards through the hole, The annular projection 75 protrudes radially outward from the government, engaging the corresponding inclined recess formed in the inner circumference of the stamper.

In particular, the inner circumference of the stamper 35 has a lower vertical wall 77 that engages the strut portion 73 of the clamp 69, an upper wall 79 that engages the outer circumference of the annular projection 75 of the clamp, and a corresponding inclined portion on the lower side of the projection 75. A mating middle inclined portion 81 is provided. This special engagement allows the stamper to be installed quickly and easily and allows the stamper to be centered with respect to the clamp. The inner circumference of the stamper can be conveniently formed on the stamper using a conventional perforator.

As shown in FIG. 7, the annular foots 53 projecting radially inwardly of each of the annular rings 41, 43 act to hold the outer periphery of the corresponding stamper 33 or 35 so that the stamper remains flat and annular cavity 31 It has a defined thickness over its entire radius. Each ring is mounted to the corresponding removable plate by a plurality of screws 83 circumferentially spaced apart.

With their specific center clamps and annular rings in place, removable plates 63, 65 are secured to their corresponding cooling platens 55, 57 by a number of fixed tabs 85 (FIGS. 1 and 4). Can be mounted relatively quickly.

The molding apparatus of another embodiment of the present invention has only a single stamper 33 'positioned on the first mold half 11', by means of the apparatus. The manufactured video disc 10 'contains information on only one of its sides. The annular ring portion of such an embodiment is shown in FIG. In this embodiment, one side of the annular cavity 31 'is formed by a stamper and the other side is formed by the outer surface 87' of the removable plate 65 'on the second mold half 17'. This surface 87 'is moderately hardened and polished, with significantly less wear and tear than with conventional dummy stampers used in conventional molding machines for making discs with information on only one side. In addition, the possibility of flaws due to foreign matter particles sandwiched under such stampers is completely prevented.

The annular ring 43 'for the second mold half can be substantially cylindrical and need not have a radially inwardly projecting annular foot, which is normally used only to retain the outer periphery of the stamper.

1, 2 and 3 show the operating sequence of the molding apparatus.

FIG. 1 shows the apparatus in the closed position in which the substrate 13 of the first die cut portion 11 and the carrier plate 15 are in press contact with each other, and the annular rings 41 and 43 of the first and second mold halves are in press contact. When in this closed position, the molten plastic disc material is injected into the annular cavity 31 between the two mold halves to form a shaped video disc 10. 2 shows the device after the device has moved to the middle, ie, the punctured position, in which the two annular rings are still in contact but the substrate and carrier plate of the first mold half are separated by a predetermined distance.

When the device is in this intermediate position a center hole is drilled in the shaped video disk. 3 shows the device after the split line between the two mold halves is open and moved to an open position in which a shaped disk with a hole in the center can be removed.

This molding apparatus is continuously moved by the molding machine (not shown) from the closed position (FIG. 1) to the intermediate or punched position (FIG. 2) and to the open position (FIG. 3). The molding machine is coupled to the molding apparatus via the substrates 13, 19 of the first and second mold halves 11, 17. The molding machine acts to reciprocate the two substrates towards and away from each other and video disk 10 is produced in a full cycle each day.

Initial separation of the two substrates 13 and 19 takes place only after the injected plastic material has cured. For the reasons described below, this initial separation movement separates the substrate 13 and the carrier plate 15 of the first mold half 11, and the dividing line passing through the annular cavity 31 remains closed. This separation acts to move the sprue bushing 39 mounted on the first mold half substrate 13 away from the shaped disk 10 to form a gap between the disk and the bushing. After these two plates are spaced apart from each other by a predetermined interval, the punch 89 is pushed upward by the air cylinder piston 91 through the shaped disk 10 into the gap between the disk and the ball bushing.

The air cylinder piston 91 is coupled to the punch by the reciprocating punch-plate assembly 93. The upwardly moving punch drills a central hole in the shaped disk in cooperation with a rigid die member 95 mounted in the central clamp 67 of the first mold half 11.

The upward movement of the punch-plate assembly 93 and the punch 89 is applied to a number of stroke limiter pins 97 which are mounted to the plate assembly and are brought into contact with the lower side of the substrate 13 of the first mold half 11. Limited by The portion of the disk 10 which is cut along all of the mouthholes 99 disposed in the mouthpiece bushing 39 to form a hole is held in place by a lower portion 101 formed in the annular recess 103 of the upper surface of the punch.

According to another feature of the invention, the dividing line is kept closed during the initial separation movement of the molding machine by a plurality of compression springs 105 arranged between the substrate 13 and the carrier plate 15 of the first mold half 11. The springs bias the carrier plate 15 in the direction of the carrier plate 21 of the first half of the second mold 17. In particular, the compression spring is formed of a solid block of polyurethane disposed in the recess 107 circumferentially spaced apart from the substrate 13.

Thus, the spring needs no maintenance. The uncompressed thickness of each spring is approximately one inch, but in the compressed state, the substrate 13 and the carrier plate 15 are bonded to reduce the thickness to approximately 3/4 inch. Perforation of the center hole to the shaped disc 10 is done when the compression spring is sufficiently compressed to resist the force of the punch 89 and keep the dividing line closely closed.

As shown in FIGS. 1 and 2, the separation movement of the substrate 13 and the carrier plate 15 of the first mold half is limited by a number of bolts. One of the bolts is shown at 109. Each bolt has a body portion 111 that extends through the through hole 113 of the substrate and engages the screw hole 115 of the carrier plate. The head of the bolt is placed in the countersink part 117 of the through hole, and after the molding machine separates the substrate and the carrier plate by a predetermined distance, the lower part of the bolt head contacts the bottom part so that two plates are further Restriction of separation.

Subsequently, the continuous movement of the molding machine acts to open the dividing line of the device as shown in FIG. 3 and makes it possible to remove the molded video disk 10.

After the device is moved to the open position (FIG. 3), the hot water 99 separated from the molded disc 10 is separated from the lower portion 101 of the punch groove 103 by the hot water outlet pin 119 actuated by the air cylinder piston 121. do.

As shown in FIG. 2, the temporary alignment of the first and second mold halves 11 and 17 with respect to each other is achieved by a number of guide pins (only one of which is represented by 25). The guide pin is provided on the substrate 13 of the first mold half 11 and engages the bushings 27 and 29 located on the carrier plate 15 of the first mold half 11 and the carrier plate 21 of the second mold half 17. . This pin-bushing arrangement cannot maintain accurate alignment between the two mold halves during long use because repeated reciprocation of the two mold halves causes at least limited wear of the pin and bushing.

According to another feature of the invention, the forming apparatus has an alignment means which does not undergo significant sliding friction during reciprocating movement of the two mold halves 11, 17. As shown in particular in FIGS. 4 and 5, such an alignment means is provided with a carrier plate of the second mold half portion 17 to engage a corresponding truncated conical recess 125 formed in the carrier plate 15 of the first mold half 11. It has a number of frustoconical struts 123 protruding outward from 21. Thus, each post is in contact with the recess only when the dividing line is closed. Only when the dividing line is closed is the correct alignment between the two mold halves made. In one embodiment, the struts and recesses are formed in the individual members attached to the sockets 127, 129 circumferentially arranged at intervals around the outer periphery of the stampers 33 and 35 of each carrier plate 15, 21.

It can be seen from the foregoing that the present invention provides an improved molding apparatus for use with a conventional injection molding machine for producing a video disc record having a central hole. The possibility of the device being subjected to wear of certain critical members and damage to the stamper's wear is minimized, and the back pressure of the air exhausted from the annular cavity of the device when molten disc material is injected, ensures that the components It is maintained at a predetermined level even without machining.

While the present invention has been described in detail with preferred embodiments, various modifications may be made without departing from the spirit and scope thereof, and thus the invention is not limited except as by the appended claims.

Claims (1)

The dividing line between the two mold halves is closed and an annular cavity is formed between the halves and a closed position in which the melt can be injected into the annular cavity to form a record disc, and the dividing line is opened and shaped First and second mold halves reciprocating relative to each other between the open positions from which the disc can be removed, a planar disc-shaped stamper mounted on one of the halves, and the first and second to form the closed position. Means for limiting the reciprocation of the second mold halves; The means is fixed to the first mold half, the first annular ring having an outwardly facing joint surface, and to the second mold half, and the first when the device is in the closed position. It has a second annular ring having an outwardly facing surface joining the joining surface of the ring, the inner circumference of the first and second ring forms the outer circumference of the annular cavity, the inner circumference of the annular ring stamper Defined by an annular root which retains its outer periphery and protrudes inwardly, the annular foot is spaced apart from the mold halves by a thickness greater than the stamper thickness so that the stamper can expand radially without substantial frictional resistance when heated by the melt injected into the cavity. And at least one of said first and second rings comprises means for venting air from said cavity when the melt is injected into the cavity. Molding apparatus for disc manufacturing.

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